Refusal
He was unwilling to do as he was instructed.
Yes, it is a real word. For example: 'He was unwilling to complete the task given'.
resisting; unwilling
unwilling to relent
loath
You get the word idle.
The antonyms of reluctant could be eager or keen. An antonym could also be excited.
Unwilling, disagreeable, unprepared.
loth
Averse.
Afraid
The word reluctant is an adjective. It means to be unwilling.